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How to build Linear PSU?
How to build Linear PSU?
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Old 19th November 2018, 09:45 AM   #11
techmate is offline techmate
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Originally Posted by FauxFrench View Post
A class A headphone amplifier, fine. 26V/0.8A I would make from a 30V/1.5A power adapter (SMPS), with 2200uF/50V at the output, followed by a linear post-regulator to reduce ripple and noise.

For the TP50 I would do the same but use a 9V/3A adapter instead.
ok sounds got, now i gotcha... let's make a list

Last edited by techmate; 19th November 2018 at 09:50 AM.
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Old 19th November 2018, 10:03 AM   #12
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Originally Posted by FauxFrench View Post
A class A headphone amplifier, fine. 26V/0.8A I would make from a 30V/1.5A power adapter (SMPS), with 2200uF/50V at the output, followed by a linear post-regulator to reduce ripple and noise.

For the TP50 I would do the same but use a 9V/3A adapter instead.
will be nice if i could pack all togheter in one box which is going to be Psu box and from there cables that will feed dac and amp
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Old 19th November 2018, 02:32 PM   #13
FauxFrench is offline FauxFrench  France
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Originally Posted by techmate View Post
will be nice if i could pack all togheter in one box which is going to be Psu box and from there cables that will feed dac and amp

Logically seen, keeping the linear regulators near the consumers (the class A headphone amp and the TP50) ensures better regulation for the power inputs. The two linear regulators may be arranged in one box. Then, the SMPS power adapters at a certain distance because they may radiate noise.
That is how I would do it.
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Old 19th November 2018, 11:31 PM   #14
FauxFrench is offline FauxFrench  France
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Originally Posted by jimk04 View Post
It works but I know it isnt correct!

I checked my DACMagic (Cambridge Audio) and I also feed it 12Vac to keep it happy. It is absolutely correct. The reason for the AC supply is probably that it is used to generate symmetrical supply voltages through single rectification. Then charge pumps are avoided.
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Old 20th November 2018, 03:25 AM   #15
techmate is offline techmate
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Originally Posted by FauxFrench View Post
Logically seen, keeping the linear regulators near the consumers (the class A headphone amp and the TP50) ensures better regulation for the power inputs. The two linear regulators may be arranged in one box. Then, the SMPS power adapters at a certain distance because they may radiate noise.
That is how I would do it.
i like you're idea, can you give me a hand in selecting all the parts that i need to accomplish the mission ?

Regards,
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Old 20th November 2018, 12:23 PM   #16
FauxFrench is offline FauxFrench  France
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Originally Posted by techmate View Post
i like you're idea, can you give me a hand in selecting all the parts that i need to accomplish the mission ?
Regards,

I will, just give me some 6 hours to remove our old kitchen (my wife's orders!) and two hours more to draw the circuits.
I'll be back.
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Old 20th November 2018, 05:40 PM   #17
jimk04 is offline jimk04  United Kingdom
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Originally Posted by FauxFrench View Post
I checked my DACMagic (Cambridge Audio) and I also feed it 12Vac to keep it happy. It is absolutely correct. The reason for the AC supply is probably that it is used to generate symmetrical supply voltages through single rectification. Then charge pumps are avoided.

Thanks for the reply.
I guess my comment was more directed at the fact that I just solely have the12v toroid and no other components.....no regulation or whatever. It is a 200VA job so shouldn't struggle to fees the DAC!

One question regarding the OPs situation....if we are to implement linear regulation to a DC supply....I can't find any ready made boards that can do 4 , 5, 6 Amps etc as may be required from a power amplifier.

Are there some out there I haven't yet landed on?

Last edited by jimk04; 20th November 2018 at 05:43 PM.
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Old 20th November 2018, 08:13 PM   #18
FauxFrench is offline FauxFrench  France
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Originally Posted by techmate View Post
i like you're idea, can you give me a hand in selecting all the parts that i need to accomplish the mission ?
Regards,
My suggestion for a 26V/0.8A linear regulator and a 5V/3A linear regulator. I chose 2200uF/35V, 220uF/35V and 22uF/35V from the needs for the 26V regulator. That voltage rating is excessive for the 5V regulator where 16V would be sufficient. However, sometimes you do not buy capacitors by the piece but in lots of 10 and then it is more practical to use few different types.

With such post regulators the ripple and step response will improve compared to your present SMPS adapters. I chose for commonly available LM317 and LM338 because they perform well and are easy to get. You can find ultra low noise regulators that will need to be put in parallel to provide sufficient current. My unqualified impression, for which I will soon be battered, is that you will not notice the difference for the actual use.
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File Type: jpg 26V_5V_Linear.jpg (58.2 KB, 628 views)

Last edited by FauxFrench; 20th November 2018 at 08:17 PM.
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Old 20th November 2018, 09:07 PM   #19
FauxFrench is offline FauxFrench  France
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Originally Posted by jimk04 View Post
Thanks for the reply.
I guess my comment was more directed at the fact that I just solely have the12v toroid and no other components.....no regulation or whatever. It is a 200VA job so shouldn't struggle to fees the DAC!

One question regarding the OPs situation....if we are to implement linear regulation to a DC supply....I can't find any ready made boards that can do 4 , 5, 6 Amps etc as may be required from a power amplifier.

Are there some out there I haven't yet landed on?
You are right, 200VA should be more than sufficient. I use only the standard 18VA. Inside, Cambridge Audio probably does as shown on the schematic - turn the 12Vac into +/- 18Vdc, symmetrical supply voltages that are then regulated down to +/- 15V. I like that design much better than having a 5Vdc input and use charge-pumps (or a micro SMPS) to bring it to +/- 5-10V. To perform the best, many high quality OP-AMPS need +/- 12-15V.

I agree with you, linear regulator kits/boards for 3-8Amp are difficult to find. Most power amplifiers run from unregulated supply voltages.

A 3-8A linear regulator is rather simple so design with an LM317 or LM337 and a 15A buffer transistor controlled by the regulator. I have made one doing +/-16V-42V, 6A and work on a +/-2-15V/3A for low power experimental use. Using a suitable IC regulator chip makes design of a linear regulator rather simple. Only if you really know your circuits, discrete power supply constructions are worth considering.
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Old 21st November 2018, 02:17 AM   #20
techmate is offline techmate
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Originally Posted by FauxFrench View Post
My suggestion for a 26V/0.8A linear regulator and a 5V/3A linear regulator. I chose 2200uF/35V, 220uF/35V and 22uF/35V from the needs for the 26V regulator. That voltage rating is excessive for the 5V regulator where 16V would be sufficient. However, sometimes you do not buy capacitors by the piece but in lots of 10 and then it is more practical to use few different types.

With such post regulators the ripple and step response will improve compared to your present SMPS adapters. I chose for commonly available LM317 and LM338 because they perform well and are easy to get. You can find ultra low noise regulators that will need to be put in parallel to provide sufficient current. My unqualified impression, for which I will soon be battered, is that you will not notice the difference for the actual use.
thank you very much you did an excellent job, will be so nice if i could print a pcb and then solder the stuff on it....ooo dreamin'.....
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